2003 ltz400 issue

[redrider74]

I have been trail riding my brothers 2003 ltz400 since my 450 has been out of commission. Last time I rode it I was beating on it pretty hard. Everything was running fine but then all of the sudden it started acting like the choke was on. It would run fine in the lower gears at low RPMs but when I got into the higher RPMs it would bog out. The next day it wouldn't start. It would pull start but it ran like crap all across the board. Now it won't start at all.

The timing chain is good, the valves are in spec, and the timing is right where it should be. It has good spark and I believe it's getting fuel. So what am I looking at here? Some sort of electrical problem or a carb issue?

How are the stators on these quads? If the stator is bad it will still produce spark, correct? What is the best way to test the stator?

Also what is the possibility of the valves being cupped?

Thanks!

[cataway]

how do you know the valves are in spec ?

[redrider74]

How does anyone know that their valves are in spec? I put the engine at TDC, took the valve cover off, and put a feeler gauge between the cam lobes and the buckets. They were in spec. That's not the problem nor is the timing or timing chain.